This invention relates to enhancement of safety in a brake system on a moving vehicle.
Where a vehicle, moving on a road that includes water, snow, ice, gravel, mud, dirt or similar substances, is brought to a sudden stop, this vehicle often skids to a stop without making a sound that might warn others about the sudden braking. On a dry pavement, a vehicle that does not include an anti-skid braking system (non-ABS) will usually produce a characteristic screeching or howling sound (from the tires and/or braking system) when the vehicle brakes suddenly. A vehicle equipped with an ABS will not produce a screeching or howling sound on any road surface.
Anti-skid braking systems (ABSs) for automobiles and other vehicles were introduced in 1978 or earlier and have become a standard feature for vehicles now manufactured. An ABS operates relatively silently to firmly apply brakes on a moving vehicle to quickly reduce the speed of a moving vehicle, or to bring the vehicle quickly to a stop, without causing vehicle spin-out or loss of control of the orientation of the vehicle. One potentially disagreeable feature of an ABS is that, due to the silent braking operation of an ABS, a pedestrian or vehicle occupant in the path of an ABS-equipped vehicle that is braking, and another vehicle traveling in the same lane behind this braking vehicle, receives no audible warning of the approaching/braking vehicle. This can be dangerous, for a non-ABS or ABS vehicle that brakes suddenly, because the pedestrian or other vehicle or vehicle occupant receives no audible warning of the action(s) taken by the braking vehicle and cannot react accordingly.
What is needed is a system that will provide an audible warning when a vehicle is braking sharply, but will not provide a spurious warning when the vehicle velocity is below a small velocity threshold that may vary with vehicle velocity, vehicle acceleration, and local road or weather conditions.
These needs are met by the invention, which provides a method and system that monitors activity of a braking system (ABS or non-ABS) on, and the present velocity of, a moving vehicle. When (1) hard braking in the braking system is activated, the system optionally determines (2) whether the moving vehicle present velocity (immediately before hard braking is applied) is at least equal to a selected velocity threshold, which can vary with the present vehicle deceleration. When both of the conditions, (1) and (2), are satisfied, the system provides an artificial, loud sound (a xe2x80x9cwarning soundxe2x80x9d WS), which resembles the screeching of brakes on a non-ABS vehicle on dry pavement when the non-ABS vehicle is being brought to an abrupt stop. xe2x80x9cHard brakingxe2x80x9d occurs when vehicle brakes are applied with substantially maximum force, above a selected force threshold.
When the braking system is activated but the vehicle velocity is below a selected velocity threshold (e.g., 0.1-5 meters/sec), the system interprets this situation as a normal (non-panic) stop from a small velocity, and the warning sound is withheld. The threshold velocity may increase as the magnitude of the vehicle deceleration increases, or where certain road or weather conditions are present. Optionally, the warning sound WS provided by the system during vehicle braking is preferentially directed in two or more selected angular sectors relative to the moving vehicle, such as a first angular sector oriented toward the front of the moving vehicle and a second angular sector oriented toward the rear of the moving vehicle, in order to provide the warning sound for those most likely to be affected by the moving vehicle as the vehicle brakes hard.
The invention is intended to reproduce the naturally occurring, universally recognized (warning) sound of screeching tires that occurs during a panic stop of a vehicle, that does not include an automatic braking system (ABS). The system responds under all weather conditions and road surface conditions and with any type of braking system. Optionally, the warning sound is not transmitted if the vehicle velocity is very low.